In the paper attention is paid to the forming of conceptual knowledge and its many-sided development in contemporary philosophical theories. First the correlation between the word and concept is elucidated on linguistic and philosophical knowledge and then the concept as a reflection of general and substantial aspects of the subject-matter is specified. Categories are considered to be the abstractions of real relationships, the unfolding schemes of human knowledge. Also mutual metamorphoses of various kinds of scientific concepts and categories in the evolution of scientific cognition are analysed. It appears that in these processes some conceptual characteristics assume the status of maximum possible abstractness and generality, but others loose it.